Screen Printing white ink well is the most important thing you can do. I’ve often said “Master white, then you have mastered screen printing.”
Here are a few thoughts before we launch right into the how to’s.
Begin with the end in mind. Know what the customer expectation is going into the project. Some customers want a super bright white. Some customers want a vintage white. Others want a soft hand print, but still have the brightness. Some customers don’t know what they want, however they sure do tell you what they like after they have the finished product in hand. That all being said do yourself a favor and just default to a super bright white as your standard and adjust if customers request anything else.
Cater to your set up. Every screen print shop is set up different. I think you can get great results no matter what you are working with. Nicer tools simply make screen printing easier. Type of automatic, manual press, exposure unit, screens, thin thread mesh, screen tensions, environment air flow heat and humidity…..all are factors that can be considered and leave room for adjustments and debate. You may even have to adjust parameters based on the season. For example printing water based ink in Chicago during the cold dry dead of winter vs screen printing during the hot humid summer are drastically different. I am going to share with you best practices, but you will adjust to your own gear, seasons, and environment.
My definition of a good white print is as follows: Bright, soft hand feel, NOT BULLET PROOF, smooth texture, not too glossy, and will hold up after washing without cracking.
PRINTING WHITE INK
I know every printer has their favorite white. Every manufacture has more white options than anybody wants to test. It is the most debated and fought over ink in the shop. I’ve seen it almost come to blows as seasoned professionals lobby for their white. I’m going to be super vanilla in this article and tell you that you can make most whites work.
All white inks have little nuance and adjustments. Some work great on press then lose their luster as they come out of a conveyor dryer. Some have additives that puff the ink, but hurt wash-fastness. Some even cure at lower temperatures, but have a glossy sticky finish due to the extra resin causing the lower cure time. I am going to focus this on a standard 320 degree curing plastisol. Should be a low cost flagship run of the mill white ink.
I do not believe in a one hit white. Even if one existed I don’t want to use it. I strongly advocate when you print white you use two screens. Their are simply too many variables that are easily solved with a second screen. From type of fabric you are printing on to simply brightening up the print, all solutions are available when you do not try to get your white perfect on the first stroke of the squeegee.
The only reason you should not use a second screen to get a perfect white print is if you are limited by your equipment or capacity for accurate registration. If these are issues and you only have one screen for white than you will want to tweak your strokes. Will go over that later in the article.
The nitty gritty nerdy details:
Screen #1: The under-base screen. This screen is the foundation for everything. I recommend 150-180 mesh count in most all cases. If half tones are involved then use a 200-230 mesh count. Getting white ink to perform through 280 mesh count+ is possible, but I would not recommend it.
The thickness of the emulsion on the shirt side of the screen will dictate how much plastisol ink is deposited on the print. For this screen I recommend using the dull edge of scoop coater at a medium pace. 2 passes on the shirt side and one final pass on the squeegee side of the screen. (2 and 1). If you still feel like you still need more ink down you can add an extra pass on the shirt side, but still make sure your last coat is on the squeegee side.
Screen #2: The highlight white screen. This screen makes everything pop. I recommend a 180-230 mesh count. If half tones are involved generally I am in a 230 or as high as 280 depending on art. I recommend using the dull edge of scoop coater at a medium pace. 2 passes on the shirt side and one final pass on the squeegee side of the screen. (2 and 1).
Waterbased ink simply needs one pass on each side with sharp edge of scoop coater. (1 and 1)
Print stroke Screen #1 technique and trouble shooting.
Our goal is to drive the ink into the fabric to produce a good foundation and gripping the garment. If printing a 100% poly shirt substitute your white ink for a dye migration blocker grey or black depending on the grade of fabric. Be sure you have plenty of adhesive holding down the garment.
Use firm pressure with at least and 1/8″ off contact. (distance between the shirt and the screen) If the screen is sticking to the shirt and not releasing right behind the squeegee you will want to raise the off contact (this could cause registration issue), get a higher tension screen, or slow down your print stroke to give the mesh time to rebound. The only time the mesh should touch the garment is when the squeegee dictates it.
Next flash dry till the ink is tacky, but won’t come off on your finger if you touch it.
Print stroke Screen #2 technique and trouble shooting.
Our goal is to make it pop. This stroke should float. Like putting peanut butter on a piece of bread. Drive the white ink through the mesh with the edge of the squeegee blade. Use just enough pressure to clear the open mesh of ink. (warm ink prints better). This technique will prevent the texture of the shirt influencing the texture of the print. If you have too heavy of a print stroke you will have rough looking prints.
“But I only have one screen for white”:
If you can only use one screen, then I here is my suggestion. Print, flash, print, but make sure you use a finishing stroke last. I would describe this final print stroke as light, quick, sharp, and accurate. Make sure ink clears the open mesh and transfers to garment. If you drive the ink through the mesh too hard you will have the influence of the garment to deal with. From color shift to rough feeling, the final stroke is where you need to dial in your process to make sure you are getting the best brightest white possible. Manual printers will be able to get away with this way easier than an automatic printer.